1. Field of the Invention
The present invention relates generally to a method for summarizing a default address of a private network-network interface lowest level node in an asynchronous transfer mode switching system, and more particularly to a method for summarizing a default address of a private network-network interface lowest level node, which is capable of summarizing the default address at the time of interfacing with a public network.
2. Description of the Prior Art
Recently, interest in Private Network-Network Interface (PNNI) effective in offering a variety of multimedia communication services and data services in an Asynchronous Transfer Mode (ATM) network is gradually being increasing.
The PNNI is a protocol for establishing an ATM Switched Virtual Connection (SVC) between ATM switching system, which was originally conceived for a private network using an ATM address in the form of a Network Service Access Point (NSAP) in the ATM forum.
PNNI routing is characterized in that the network configuration of a hierarchical structure is enabled and dynamic routing is supported. Here, the hierarchical structure is referred to as a network structure in which more than one node are tied into a plurality of peer groups which are further tied into a plurality of upper level peer groups. The dynamic routing is referred to as the establishment of a connection by source routing based on topology information distributed between switching system. The hierarchical structure allows the large network scalability, and the dynamic routing allows the efficient use of a network resource.
Nevertheless, as an ATM switching system tends to be connected to various kinds of networks when it is actually constructed, there exists a need for the PNNI to be smoothly applied to not only private networks but also public networks.
However, when the PNNI is applied to the public networks, there occurs a problem that the default address summarized according to the specification of the PNNI cannot be used as it is in the public networks, which will be further discussed below.
In the switching system using the PNNI, as part of the dynamic routing, reachable addresses for nodes should be dynamically exchanged between the switchers during operation of the system. On the other hand, since the PNNI has a hierarchical structure, there is a need to reduce overhead in exchange of information through a large network. To this end, PNNI specification 1.0 defines prefix information of 13 octets length, i.e., 104 bytes, with respect to default address summarization regarding a node address. As mentioned earlier, the PNNI was originally conceived for the private networks. When such PNNI is applied to the public networks and the prefix information of 13 octets length with respect to default address summarization is used, there occurs a problem that the point of default address summarization cannot be applied to the public networks. This is because the prefix information of 13 octets length can merely distinguish subscriber numbers in the public networks due toe poor application of the default address summarization function in the public networks, though it can distinguish one private network from another private network. Then, when the PNNI is applied to the public networks, since the default address summarization function is not properly operated and so the information on the reachable address becomes enormous, there is a problem that the public networks suffers from overload.
As a prior art for the PNNI, Korean patent laid-open No. 2001-38485 entitled “A method for reducing nodes in PNNI” is disclosed.
The object of the above prior art is to use more efficiently the network to which the PNNI is applied and reduce the probability of failure at the time of selecting a connection path by reducing node information by use of complex node representation properly reflecting the characteristics of nodes and links within the peer groups.
In order to accomplish the above object, the prior art is characterized in that it comprises the steps of searching edge nodes within peer groups and defining the edge nodes reflected in internal links as ports of complex nodes, identifying parameters defining the state of each of the ports, and constructing radius, exception, and bypass for the identified parameters.
However, the described prior art describes only summarization of the information on nodes and links within peer groups of the network to which the PNNI is applied, but is not contemplated for an application to the public networks. In addition, even when the PNNI is applied to the public networks, the default address summarization of the lowest level node is not described at all, and even any relevance to the default address summarization is not mentioned therein.